Field of the Disclosure
The present disclosure, for example, relates to wireless communication systems, and more particularly to techniques for adaptively enabling a synchronization of nodes that are using a Listen Before Talk (LBT) Load-Based Equipment (LBT-LBE) protocol to contend for access to a shared radio frequency spectrum band.
Description of Related Art
Wireless communication systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include code-division multiple access (CDMA) systems, time-division multiple access (TDMA) systems, frequency-division multiple access (FDMA) systems, single-carrier frequency-division multiple access (SC-FDMA) systems, and orthogonal frequency-division multiple access (OFDMA) systems.
By way of example, a wireless multiple-access communication system may include a number of base stations, each simultaneously supporting communication for multiple communication devices, otherwise known as user equipments (UEs). A base station may communicate with UEs on downlink channels (e.g., for transmissions from a base station to a UE) and uplink channels (e.g., for transmissions from a UE to a base station).
Some modes of communication may enable communications between a base station and a UE over a shared radio frequency spectrum band, or over different radio frequency spectrum bands (e.g., a licensed radio frequency spectrum band or a shared radio frequency spectrum band) of a cellular network. With increasing data traffic in cellular networks that use a licensed radio frequency spectrum band, offloading of at least some data traffic to an unlicensed radio frequency spectrum band may provide a cellular operator with opportunities for enhanced data transmission capacity. An unlicensed radio frequency spectrum band may also provide service in areas where access to a licensed radio frequency spectrum band is unavailable.
Prior to gaining access to, and communicating over, an unlicensed radio frequency spectrum band, a base station or UE may perform an LBT procedure to contend for access to the unlicensed radio frequency spectrum band. An LBT procedure may include performing a clear channel assessment (CCA) procedure to determine whether a channel of the unlicensed radio frequency spectrum band is available. When it is determined that the channel of the unlicensed radio frequency spectrum band is available, a channel usage beacon signal (CUBS) may be transmitted to reserve the channel.
In some cases, transmissions by one or more nodes over a shared radio frequency spectrum band (e.g., Wi-Fi nodes, nodes of other operators, or unsynchronized nodes of a same operator) may prevent a base station or UE from winning contention for access to the shared radio frequency spectrum band, resulting in the base station or UE being “starved” of access to the shared radio frequency spectrum band. In some cases, this starvation problem may be mitigated by using an LBT protocol configured for load based equipment (LBT-LBE), instead of an LBT protocol configured for frame based equipment (LBT-FBE), when contending for access to the shared radio frequency spectrum band. When using an LBT-LBE protocol to contend for access to the shared radio frequency spectrum band, an extended CCA procedure including a plurality of N CCA procedures, with N being a random integer between 1 and q, may be performed. The extended CCA procedure may provide a base station or UE a better chance to win access for contention to the shared radio frequency spectrum band (e.g., compared to a single CCA procedure performed in conjunction with an LBT-FBE protocol).